1. Field of the Invention
This invention relates to an improved safety landing which is used to divide a vertical shaft or manhole at predetermined positions.
2. Description of the Prior Art
Safety landings, safety platforms and safety gratings are common terms used to describe a supporting subfloor which is fixed at various elevations to divide a vertical shaft or manhole into separate areas.
Safety landings are used for various purposes. They will limit the vertical distance that a falling object is allowed to fall before it is stopped by the safety grating. Thus, if a workman drops a tool, the tool will be stopped by the safety landing to make its retrieval easier. More importantly, if a workman slips while climbing up or down the vertical shaft, his fall will be interrupted by the safety landing which in many cases, saves the life of the workman or reduces the possible injury which results from the fall.
Safety landings are also used to interrupt long vertical climbs or descents by workmen by providing a platform transition area for the workman before he continues his climb or descent.
Also, by limiting the vertical climbing or descent distance to a safe height, the workman must stop his ascent or descent at each safety landing to open or close the landing. This forces the workmen to rest at the safety landing and reduces significantly, the fatigue created by long ascents and descents. By doing so, a significant reduction in accidents has occurred due to fatigue of the workman.
The safety landing also provides a dry working floor area above liquid or waste filled shafts or manholes as well as providing a working platform to enable the workman to perform various tasks and jobs in the shaft or manhole such as pump maintenance and reading gauges.
In designing a safety landing, its operation must be standardized so that it is easy for the workman to operate in a similar fashion to the conventional grate. It must have a positive means for controlling access to various levels in the manhole and also, it must be easy enough for the operator to operate but not so easy to allow a workman to tamper with its safety features to circumvent these features. The landings must have sufficient strength to carry different types of loads, particularly for heavy machinery which may be placed in the landing when the landing is used as a working platform. The landing must also be strong enough to withstand continuous use over a long period of time without failing.
The prior art devices usually comprise a pair of panels, each panel comprising a plurality of platform rungs usually made of aluminum. The pair of panels are placed side by side and the opposite ends of the panels are pivotally attached to a support. The support is driven into the manhole wall when the concrete is still green.
Each panel may be pivoted independently to the vertical position and affixed to the wall of the manhole by a snaphook and chain. In its installation, these devices must be aligned exactly with respect to the elevation of the device and also with respect to its orientation.
Also, the manner of installation is both cumbersome and time consuming. The use of a hook and chain (as found in the prior art devices) to maintain the panel in the upright position and the use of a J-bolt to lock the panel in the horizontal position requires extra labour in installation and their use cannot be ensured by the workman. With these devices, it is possible for workmen to circumvent these means which may result in an unfortunate accident. The support has also required a great amount of concrete displacement for its installation and the restrictive tolerances demand great care and dimensional control during installation.